1. Field of the Invention
The invention relates in general to a plasma system, and more particularly to a plasma system capable of preventing the electrodes from being damaged.
2. Description of the Related Art
Along with the prosperity in the semiconductor industry, various manufacturing methods, processes and facilities are developed and used. Plasma can perform surface treatment such as surface cleaning, surface etching, trench etching, thin film deposition and hydrophilic treatment, and hydrophobic treatment on the surface of a substrate. Examples of plasma processing facility include plasma cleaning, plasma enhance chemical vapor deposition (PECVD), plasma enhance reactive ion etching (PERIE), micro wave plasma oxidation, micro wave plasma nitridation, ionized metal plasma (IMP) and sputter deposition.
Despite the plasma is electrically neutral, there are many particles with different potentials in the atmosphere of plasma. Examples of particles include atoms, free radicals, ion, molecules, molecule free radicals, polarized molecules, electrons and photons. The particles are generated inside the reaction chamber of plasma facility. There are positive and negative electrodes disposed inside the reaction chamber. When the gas between positive and negative electrodes is driven by the voltage between two electrodes, the gas is dissociated and plasma is generated.
However, the electrodes disposed inside the reaction chamber will be polluted or eroded by plasma particles and then become damaged. When the electrodes are damaged, plasma stability as well as the quality of plasma products will be affected. As plasma facility is a constant-pressure system, an expensive carrying platform is needed if the range of plasma treatment is to be expanded. Furthermore, the constant-pressure system normally requires a higher power for driving plasma, that is, the plasma is driven by either a large current or a large voltage. When the current or the voltage is too large, heat problem such as electrode deformation will occur.